Pseudomonas aeruginosa is an opportunistic bacterial pathogen that causes chronic lung infections associated with biofilm formation in the airways of cystic fibrosis (CF) and immune-compromised patients, including those with chronic wounds. Biofilms are structured communities of microbes encased within a matrix and exhibit resistance to antimicrobials and host defenses. It remains unclear how biofilm bacteria survive within the CF airways or the interplay of P. aeruginosa matrix materials with host immune cells. The focus of this application is on two critical components of the P. aeruginosa biofilm matrix biofilm matrix, an extracellular polysaccharide Psl and a protein adhesion CdrA. Our overall objective is to determine the roles of Psl and CdrA in biofilm structural integrity and tolerance o P. aeruginosa to antimicrobials and host defense. Aim 1 will focus investigating structure- function relationships necessary for P. aeruginosa biofilm matrix integrity and define the roles of biofilm matrix components in modulating interactions of P. aeruginosa with human phagocytic cells. In the second aim we will define a novel signal transduction pathway responsible for a feed-forward mechanism of Psl-dependent signaling. There remain significant gaps in our understanding of how P. aeruginosa survive in the CF airway even in the presence of a robust immune response. Since the biofilm matrix provides a protective role, studies aimed at understanding the functions of matrix components will provide insights and therapeutic strategies aimed at early events of CF pathogenesis and other P. aeruginosa infections where biofilms are linked with human disease.